1. Field of the Invention
The present invention relates to a frame structure for a vehicle provided with wheels on the left and right sides of a vehicle body, such as an All Terrain Vehicle (ATV).
2. Description of the Background Art
In the vehicle frame art, a frame structure is known in which the rear portion of a vehicle body frame is formed as a sub-frame, and an independent rear suspension is supported by the sub-frame. Such a frame structure is disclosed, for example, in JP-A-2001-328410. As seen in FIG. 5 of that document, a sub-frame is disclosed which includes upper and lower separate frame members, and the lower frame member is formed into a substantially L-shape as viewed in a side view by bending and extending the rear portion thereof upward, and the rear end portion of the upper frame member is connected to a vertically intermediate portion thereof. One end side of upper and lower suspension arms of the rear suspension are supported by the upper and lower frame members. Further, a dedicated supporting pipe for supporting a terminal gear case which is arranged inside the sub-frame extends between the upper and lower frame members.
In the above-mentioned publication, members that require accuracy and rigidity are concentrated on a suspension supporting portion (sub-frame) of the vehicle body frame and, in addition, these members are required to have special shapes or parts respectively and hence, the structures of these members tend to become complicated. In view of this, a suspension supporting portion is desired in which the constituent members are simplified and less complicated.
Accordingly, the invention provides a frame structure in which accuracy and rigidity of a suspension supporting portion of a vehicle body frame are easily ensured, and the structure is simplified.